SECTION 2: CHASSIS

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Nov 2, 2013 (4 years and 1 month ago)

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SECTION 2: CHASSIS

2.1 Definition
2.2 Welding
2.3 Definition of Chassis Modifications
2.4 Chassis Types
2.5 Chassis Frame Construction
2.6 Chassis Strengthening and Crossmembers
2.7 Nuts Bolts and Fasteners
2.8 Chassis Illustrations


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2.1 DEFINITION

2.1.1 All Street Rods must have a chassis. A chassis is defined as a structural unit that
will support the full load of the vehicle drive train, body and all ancillary
components. The body and chassis are detachable by means of standard
fasteners and the chassis must not rely on the body for strength. A number that
identifies the chassis must be stamped on the chassis.

2.1.2 A Street Rod chassis needs to be a platform that resists twisting. A torsionally
rigid chassis will not only be stronger and last longer, but will also provide better
handling and allow closer fit-up of body panels.


2.2 WELDING
2.2.1 A novice must not carry out the construction or modification of a chassis.
Numerous effects such as twisting and loss of strength can be caused by incorrect
penetration, preparation, or timing of weld deposits. Inspection of all welds and
the requirement for rework will be at the discretion of the Examiners. Structural
chassis welding is recommended to be carried out with the chassis fixed in a jig.
An example of a chassis jig is shown in diagram 2 (a) on the next page.

{Advisory Note: Those persons who have experience, but do not possess
certification, are advised to attend a TAFE or Private Provider Certified welding
course.}

2.3 DEFINITIONS OF PRACTISES USED IN CHASSIS MODIFICATIONS
2.3.1 Boxing
The addition of a 3mm or thicker plate welded into the opening of a “C” channel to
form a box section. This section can either be the full length of the side rail, or
added to areas requiring extra strength. Boxing plate attachment should be
carried out as shown in diagrams 2(c) and 2(d) at the end of this section.

2.3.2 Laminating
The attaching of an additional 3mm or thicker plate to a chassis side rail. Large
lamination plates may require the addition of plug welds to ensure full contact with
side rails.

2.3.3 Gusseting
A gusset is usually triangular in shape and is connected between butt welded
chassis parts. An example of gusseting is given in diagram 2(e).

2.3.4 Fish-Plates
A fish-plate is similar to a lamination plate, and is affixed when a gusset cannot be
easily utilised, or a vertical slice, pie cut or section has been removed and the
parts are butt welded together. Fish-plates should be twice as long as the chassis
vertical height with triangular extensions to increase weld length and purchase
area. An example of a “fish-plate” is shown in diagram 2(f).

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Diagram 2(a) Example of a chassis jig.



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2.4. CHASSIS TYPES
2.4.1 Chassis may be accepted in the following forms provided that the criteria in each
instance can be met.

2.4.1.1 Original Pre-1949 Manufactured - Modified
These chassis represent the bulk of street rod foundations, and specific
recommendations for strength enhancement are detailed in Clause 2.6 of
this section.

2.4.1.2 Reproduction - Australian Professional Rod Shop
Most reproduction chassis made by Australian Manufacturers are able to
comply with the requirements of these guidelines. All chassis must be
presented for a first build inspection by the Examiners and are required
to comply with these Guidelines.

2.4.1.3 Reproduction - Overseas Rod Shop
US or NZ manufacturers may not be aware of the Australian
requirements, for example minimum crossmember thickness of 3mm,
and should be checked thoroughly prior to purchase. All overseas built
chassis must be presented for a first inspection and must comply with
these Guidelines.

2.4.1.4 Owner Built Reproduction
An owner built chassis must comply with the requirements of these
Guidelines and may require an engineer’s report for components such as
independent front suspensions and any radical chassis alterations.
Examiners may accept any chassis construction providing sound
engineering principles have been applied. Where there is any concern
about the strength or integrity of a chassis, the Examiner may request an
engineers report addressing the concern.


2.5 CHASSIS FRAME CONSTRUCTION
2.5.1 The minimum requirement for a chassis that will support a light bodied vehicle (T-
Bucket, Anglia etc) is 75 x 50 x 3mm rectangular hollow section (RHS) mild steel.

2.5.2 The minimum requirement for a chassis that will support heavier vehicles, such as
an A model or later Ford, is 100 x 50 x 3mm RHS steel tubing, or tubing of a cross
section no less than the original production chassis.

2.5.3 Space frame and other chassis designs are permitted provided that an engineers
report is produced if requested by the Examiner. Where there is any concern
about the strength or integrity of a chassis, the Examiner may request an
engineers report addressing the concern.

2.5.4 All Street Rods must be fitted with a tailshaft loop to contain the tailshaft in the
event of front yoke failure. A tailshaft loop should be positioned no more than
150mm from the front yoke and be constructed so that it will withstand the force of
a errant tailshaft that has broken free. The tailshaft loop may be formed as part of
the centre crossmember.

2.5.5 Chassis stepped in at the rear to accommodate wheel rims wider than 10” are not
permitted.


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2.6 CHASSIS STRENGTHENING AND CROSSMEMBERS
2.6.1 The addition of partial or full boxing, lamination of side rails, and the addition of
space frame attachments are all suitable means of chassis side rail strength
improvement. Full length boxing is highly recommended on all C-section chassis.
An Engineer’s report may be required if a C-section chassis is not boxed.

2.6.2 The modification of an early model chassis often includes the full or partial removal
of original crossmembers. The minimum requirement after removal of an original
crossmember is to install a “K” member. The desired layout of a “K” member and
other crossmember types and alterations are depicted in diagrams 2(g) and 2(i) at
the end of this section.

2.6.3 All crossmembers must have a minimum wall thickness of 3mm with an
appropriate cross-section. The preferred size is 75 x 50mm RHS if one layer is
used, or 50 x 25mm or round tube of at least 37mm diameter if two layers are
used with ties between the upper and lower layer in appropriate locations.

2.6.4 Chassis crossmembers for engine and drivetrain location may be removable if
desired. Ensure that flange plates and bolts used are suitably sized, and that nuts
or threaded bosses have enough thread depth for the application.

2.6.5 Any centre crossmember needs to tie together both side rails to ensure torsional
rigidity. Refer to the diagrams at the end of the section to ensure that your chassis
will be sufficiently rigid. Vintage chassis were not designed as a rigid platform and
allowed the chassis and body to flex independently. This is undesirable in a street
rod as damage to paint finishes will result from flexing, and ride comfort and safety
will be reduced.

2.6.6 Spacer tubes, crush tubes, or stepped bolts must be used wherever a bolt passes
through a hollow section of the chassis. The tube should be 3mm or larger wall
thickness and welded in position. The following diagram 2(b) shows examples of
spacer tubes.



Diagram 2(b)


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2.7 NUTS BOLTS AND FASTENERS

2.7.1 Tabled below are the minimum standards acceptable for the choice of nuts and
bolts used in Street Rods.

2.7.1.1 Ungraded bolts - Panel fixing, floor panel fixing, and lightly loaded
brackets.

2.7.1.2 Grade 3 bolts - Seat belts.

2.7.1.3 Grade 5 bolts - Moderately loaded members, suspension mounts,
crossmembers and tailshafts.

2.7.1.4 Grade 8 bolts - Brake callipers, master and slave cylinder mounts,
steering arms and all heavily loaded assemblies.

Note that high grade bolts are not to be used as seat belt bolts. It is a
requirement that only bolts designed specifically for seat belts be used in
this application.

2.7.2 Stainless steel bolts are not to be used in high load or stressed situations as they
do not possess high tensile strength. It is recommended that these bolts be used
in locations where the use of ungraded bolts is permitted.

2.7.3 The bolt or fastener should be long enough to ensure that at least one clear turn
of thread is visible. This applies to all nuts, including nyloc and locking nuts.

2.7.4 Locking devices must be fitted to all fasteners. These devices include:

• Spring and shakeproof washers.

• Nyloc nuts.

• Deformed thread locknuts or Huck nuts.

• Castellated nuts with split or roll pins.

• Lockwire.

• Split pins.

• Locking Tabs, and staking.

2.7.5 Nyloc nuts are only to be reused once, and only if the nylon locking area is in good
condition.

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2.8 CHASSIS ILLUSTRATIONS

Diagram 2(c) Example of Internal Boxing Diagram 2(d) Example of External Boxing


Diagram 2(e) Example of Gusseting Diagram 2(f) Example of a Fish Plate





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Diagram 2(g) Example of “K” member
Diagram 2(h) Example of “X” member

Diagram 2(i) Example of a Tubular “X” member

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